U.S. patent application number 10/893860 was filed with the patent office on 2005-12-08 for flat wide-angle objective.
Invention is credited to Faybishenko, Victor, Gurevich, Igor, Velikov, Leonid.
Application Number | 20050270667 10/893860 |
Document ID | / |
Family ID | 46302372 |
Filed Date | 2005-12-08 |
United States Patent
Application |
20050270667 |
Kind Code |
A1 |
Gurevich, Igor ; et
al. |
December 8, 2005 |
FLAT WIDE-ANGLE OBJECTIVE
Abstract
A flat wide-angle objective of the invention consists of a first
sub-unit that is located on the object side of the objective and
comprises an assembly of two conventional aspheric negative, e.g.,
aspheric piano-concave lenses, and a second sub-unit in the form of
a set of four microlens arrays arranged on the image-receiving side
of the objective. The microlenses of all microlens arrays have the
same arrangement of microlenses in all the arrays. A diaphragm
array with restricting openings can be sandwiched between a pair of
the microlens arrays. The objective of the invention can be
realized into an optimal design only with predetermined
relationships between the parameters of the optical system that
forms the objective. The invention makes it possible to drastically
reduce longitudinal dimension of the objective. In operation, the
first sub-unit creates an imaginary image of the object in its
focal plane, which is located on object side of the objective,
while the second sub-unit creates an actual image of the object in
the image plane on the image-receiving side of the objective. In
this case, the function of the object plane is fulfilled by the
aforementioned focal plane of the first sub-unit that contains the
imaginary image of the real object.
Inventors: |
Gurevich, Igor;
(Saarbrucken, DE) ; Faybishenko, Victor; (Union
City, CA) ; Velikov, Leonid; (San Carlos,
CA) |
Correspondence
Address: |
Leonid Velikov
1371 Greenbrier Rd.
San Carlos
CA
94070
US
|
Family ID: |
46302372 |
Appl. No.: |
10/893860 |
Filed: |
July 19, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10893860 |
Jul 19, 2004 |
|
|
|
10862178 |
Jun 7, 2004 |
|
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Current U.S.
Class: |
359/754 |
Current CPC
Class: |
G02B 13/06 20130101;
G02B 3/0056 20130101; G02B 13/18 20130101; G02B 3/0068
20130101 |
Class at
Publication: |
359/754 |
International
Class: |
G02B 009/00 |
Claims
What we claim is:
1. A flat wide-angle objective for creating a real image of an
object, said flat wide- angle objective having an object side and
an image-receiving side and comprising: a first sub-unit located on
said object side, said first sub-unit having a focal plane on said
object side and comprising at least two negative aspheric lenses
that create an imaginary image of said object in said focal plane;
and a second sub-unit located on said image-receiving side having
an image plane of said flat wide-angle objective on said
image-receiving side and comprising a set of microlens arrays; said
second-sub-unit having an object plane that coincides with said
focal plane of said first-sub-unit so that said second sub-unit
forms said real image of said object in said image plane of said
flat wide-angle objective.
2. The flat wide-angle objective of claim 1, wherein said two
negative aspheric lenses comprises a first negative aspheric lens
and a second negative aspheric lens, both having flat surfaces that
face said object side and concave surfaces that face said
image-receiving side, said first negative aspheric lens and said
second negative aspheric lens having interrelated dimensions,
relative positions and curvatures selected so as to provide
formation of said imaginary image in said focal plane.
3. The flat wide-angle objective of claim 2, wherein said second
sub-unit comprises a set of at least four microlens arrays
consisting of a first microlens array, a second microlens arrays, a
third microlens arrays, and a fourth microlens array, each said
microlens array having a plurality of microlenses having the same
pitch between said microlenses and the same arrangement of said
microlenses in each of said microlens arrays, said second microlens
array and said third microlens array having said microlenses
thereof facing in mutually opposite directions with said
microlenses of said second microlens arrays facing said object side
and said with said microlenses of said third microlens array facing
said image-receiving side; said first microlens arrays and said
fourth microlens array being identical and having a symmetrical
arrangement with respect to said second micro lens array and said
third microlens array; said microlenses of said first microlens
array and said fourth microlens array having their curvatures
different from curvatures of said microlenses of said second
microlens array and said third microlens array.
4. The flat wide-angle objective of claim 3, wherein said
microlenses have an arrangement selected from a hexagonal-lattice
arrangement and a square-lattice arrangement with hexagonal or
square shapes of said microlenses.
5. The flat wide-angle objective of claim 4, further comprising a
diaphragm array sandwiched between said second microlens array and
said third microlens array, said diaphragm array having openings
arranged with the same pitch and with the same arrangement as said
microlenses.
6. The flat wide-angle objective of claim 5, wherein said openings
of said diaphragm array have a diameter equal to or smaller than a
diameter of a circle inscribed into said microlenses of said second
microlens array and said third microlens array.
7. The flat wide-angle objective of claim 4, wherein each group of
microlenses which are aligned and are located in said first
microlens arrays, said second microlens array, said third microlens
array, and said fourth microlens array forms a unit microlens cell
for propagating a beam of light in the direction from said object
to said image plane.
8. The flat wide-angle objective of claim 5, wherein each group of
microlenses which are aligned and are located in said first
microlens arrays, said second microlens array, a respective opening
of said diaphragm array, said third microlens array, and said
fourth microlens array form a unit microlens cell for propagating a
beam of light in the direction from said object to said image
plane.
9. The flat wide-angle objective of claim 3, wherein said first
microlens array, said second microlens array, said third microlens
array, and said fourth microlens array have interrelated
dimensions, relative positions, and curvatures of microlenses
thereof selected so as to provide formation of said real image of
said object in said image plane.
10. The flat wide-angle objective of claim 4, wherein said first
microlens array, said second microlens array, said third microlens
array, and said fourth microlens array have interrelated
dimensions, relative positions, and curvatures of microlenses
thereof selected so as to provide formation of said real image of
said object in said image plane.
11. A flat wide-angle objective for creating a real image of an
object, said flat wide-angle objective having an object side and an
image-receiving side and comprising: a first sub-unit located on
said object side, said first sub-unit having a focal plane on said
object side and comprising two plano-concave aspheric lenses that
create an imaginary image of said object in said focal plane; and a
second sub-unit located on said image-receiving side having an
image plane of said flat wide-angle objective on said
image-receiving side and comprising a set of microlens arrays; said
second-sub-unit having an object plane that coincides with said
focal plane of said first-sub-unit so that said second sub-unit
forms said real image of said object in said image plane of said
flat wide-angle objective with an image-transfer ratio of 1:1.
12. The flat wide-angle objective of claim 11, wherein said two
negative aspheric lenses comprises a first negative aspheric lens
and a second negative aspheric lens, both having flat surfaces that
face said object side and concave surfaces that face said
image-receiving side, said first negative aspheric lens and said
second negative aspheric lens having interrelated dimensions,
relative positions and curvatures selected so as to provide
formation of said imaginary image in said focal plane.
13. The flat wide-angle objective of claim 12, wherein said second
sub-unit comprises a set of four microlens arrays consisting of a
first microlens array, a second microlens arrays, a third microlens
arrays, and a fourth microlens array, each said microlens array
having a plurality of microlenses having the same pitch between
said microlenses and the same arrangement of said microlenses in
each of said microlens arrays, said second microlens array and said
third microlens array having said microlenses thereof facing in
mutually opposite directions with said microlenses of said second
microlens arrays facing said object side and said with said
microlenses of said third microlens array facing said
image-receiving side; said first microlens arrays and said fourth
microlens array being identical and having a symmetrical
arrangement with respect to said second micro lens array and said
third microlens array; said microlenses of said first microlens
array and said fourth microlens array having their curvatures
different from curvatures of said microlenses of said second
microlens array and said third microlens array.
14. The flat wide-angle objective of claim 13, wherein said
microlenses have an arrangement selected from a hexagonal-lattice
arrangement and a square-lattice arrangement with hexagonal or
square shapes of said microlenses.
15. The flat wide-angle objective of claim 14, further comprising a
diaphragm array sandwiched between said second microlens array and
said third microlens array, said diaphragm array having openings
arranged with the same pitch and with the same arrangement as said
microlenses.
16. The flat wide-angle objective of claim 15, wherein said
openings of said diaphragm array have a diameter equal to or
smaller than a diameter of a circle inscribed into said microlenses
of said second microlens array and said third microlens array.
17. The flat wide-angle objective of claim 14, wherein each group
of microlenses which are aligned and are located in said first
microlens arrays, said second microlens array, said third microlens
array, and said fourth microlens array forms a unit microlens cell
for propagating a beam of light in the direction from said object
to said image plane.
18. The flat wide-angle objective of claim 15, wherein each group
of microlenses which are aligned and are located in said first
microlens arrays, said second microlens array, a respective opening
of said diaphragm array, said third microlens array, and said
fourth microlens array form a unit microlens cell for propagating a
beam of light in the direction from said object to said image
plane.
19. The flat wide-angle objective of claim 13, wherein said first
microlens array, said second microlens array, said third microlens
array, and said fourth microlens array have interrelated
dimensions, relative positions, and curvatures of microlenses
thereof selected so as to provide formation of said real image of
said object in said image plane.
20. The flat wide-angle objective of claim 14, wherein said first
microlens array, said second microlens array, said third microlens
array, and said fourth microlens array have interrelated
dimensions, relative positions, and curvatures of microlenses
thereof selected so as to provide formation of said real image of
said object in said image plane.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The present patent application is a continuation in part of
U.S. patent application Ser. No. 10/862,178 filed by the same
applicants on Jun. 7, 2004 and entitled "Flat Wide-Angle Lens
System".
FIELD OF THE INVENTION
BACKGROUND OF THE INVENTION
[0002] The present invention relates to the field of optics and,
more particularly, to a wide-angle flat photographic lens
objective. More specifically, the invention relates to a wide-angle
flat photographic lens system which is built on an entirely new
principle of combining a group or groups of flat microlenses with a
group or groups of conventional optical lenses. The lens system of
the invention may find application in photographic cameras, image
projection systems, etc.
BACKGROUND OF THE INVENTION
[0003] For better understanding the terminology used in the present
description and principles of structure of optical systems in
general, it would be advantageous to make some short introduction
into the field of optical objectives.
[0004] An objective is an optical system or a part thereof that
faces an object of observation or photographing and that creates a
real image of the object turned 180.degree. with respect to the
object. Depending on the types of optical elements, objectives can
be divided into lens-types, mirror-types, mirror-lens-types, and
kinoform-type objectives. Most popular are lens-type objectives
that are capable of acquiring various characteristics due to
increase in the number of component lenses.
[0005] Photographic objectives or similar objectives of
motion-picture cameras, TV cameras, night-vision instruments, and
objectives used in television generally create reduced images of
remote objects on a layer of a photosensitive material or on
photoreceivers, e.g., TV picture tubes, matrices or linear
photoreceivers, or photocathodes of optoelectronic devices. The
scale of an image is proportional to a focal distance f' of the
objective, while illumination intensity is inversely proportional
to a second power of a diaphragm number K, which is an f/D ratio
where D is a diaphragm of an inlet pupil of the objective. A value
of 1/K is known as an aperture ratio. The limit value of the
diaphragm number that allows correction of aberrations is K=0.5. A
majority of existing objectives have K within the range of
3>K.gtoreq.1.2. Photographic resolution capacity N.sub.f of
photo and motion-picture objectives depends on aberrations, as well
as on resolution capacity N.sub.c of the photosensitive layer of
the reproducing medium and can be calculated with the use of the
following approximated formula: 1/N.sub.f=1/N.sub.0+1/N.sub.c,
wherein N.sub.0 is a visual resolution capacity of the objective.
In a lens system, aberration is an error resulting from a failure
of light rays from one point to converge to a single focus. A part
of a space or surface the points of which are reproduced by the
objective with a required quality is characterized by an angular
field, i.e., a flat angle 2.omega. that corresponds to a solid
angle that is coaxial with the optical axis and has the apex in the
center of the inlet pupil of the objective. Angular field of modern
photo cameras is normally within the range of 400 to 70.degree.,
while in aerophoto cameras this angle may reach 140.degree..
[0006] A special group is objectives, which are also known as zoom
lenses, the focal distance of which can be smoothly adjusted in a
wide range by displacing separate lenses or groups of lenses along
their optical axis. The number of lenses in such objectives may be
as high as 30 or more. Such objectives are used, e.g., in
transmission TV cameras, video cameras, and photo cameras. A ratio
between the maximal and minimal focus distances may reach 40, or
more. For decrease of optical losses, modern objectives are
provided with anti- reflective coatings.
[0007] Normally, conventional wide-angle photographic objectives or
lens systems have big dimensions, i.e., a lengthy objective, and
therefore are inconvenient for use and storage. Another
characteristic feature of a wide-angle photographic lens system is
an increased diameter. This not only increases the overall radius
and hence the dimension of the lens system but also significantly
increase the weight of the objective as a whole.
[0008] There exist a large number of wide-angle photographic lens
systems of different types, e.g., conventional photographic lens
systems for photo cameras, image projecting lens systems,
wide-field lithography systems, etc.
[0009] For example, U.S. Pat. No. 4,188,092 issued in 1980 to Kikuo
Momiyama describes a retrofocus type lens for a photo camera having
an angle of view at least 75.degree. and F number 1:2.0. The lens
includes a first lens group of a divergent type, a second lens
group of a convergent type, and a third lens group of a convergent
type. The first lens group includes in the order stated a positive
meniscus lens, a negative meniscus lens, a positive meniscus lens,
and a negative meniscus lens. The second lens group includes a
positive lens, which is either a single lens or consists of a
positive lens, and a negative lens cemented to each other and with
a front convex face directed toward an object to be photographed.
The third lens group includes a positive lens having a rear convex
face directed toward an image of the object, a biconcave lens with
its front surface radius smaller than its rear surface radius, a
positive meniscus lens with a convex surface facing the image, and
a positive lens. The biconcave lens and the positive meniscus lens
are respectively replaceable with cemented doublet lenses. The lens
system is characterized in that the first lens group includes
meniscus lenses arranged in the order of positive, negative,
positive and negative lenses, and particularly in that the third
positive meniscus lens serves effectively to correct chromatic
distortion aberration and chromatic coma aberration.
[0010] Another example, e.g., U.S. Pat. No. 6,084,719 issued in
2000 to Saburo Saguwara, et al. discloses a projection optical
system that includes a first lens unit in which negative lenses
included therein are larger in number than positive lenses included
therein, and a second lens unit in which positive lenses included
therein are larger in number than negative lenses included therein.
In this projection system, design parameters are determined such
that an off-axial principal ray intersects an optical axis at a
point between the first lens unit and the second lens unit, and
telecentricity is made on the second conjugate point side. The
second lens unit includes a negative lens of meniscus form convex
toward the second conjugate point side and a positive lens whose
both surfaces are convex.
[0011] A common problem associated with wide-angle lens systems of
the types described above as well as with other conventional
wide-angle lens systems is that an increase in the aperture ratio
of the lens system, widening of the field of observation, and
improvement in resolution capacity of the optical system require an
increase in the lens diameter. However, such an increase leads to
more noticeable aberrations, and in order to solve the aberration
problem, it is necessary to introduce into the system new optical
elements. However, Increasing the number of lens elements to
overcome the above-described drawbacks degrades the performance of
the lens system due to adverse effects such as flare. All this
significantly increases the manufacturing cost and the cost of the
products.
[0012] Attempts have been made to solve the above problems and to
improve conventional wide-angle lens systems, e.g., by increasing
the amount of optical elements.
[0013] For example, U.S. Pat. No. 5,790,324 issued in 1998 to
Cheon-Ho Park describes a wide-angle photographic lens system in
which improvement in optical characteristics is achieved at the
expense of complexity, increased weight, and increased cost. More
specifically, the aforementioned lens system consists of seven lens
elements, including combined lens elements.
[0014] One of the latest patents in this field, i.e., U.S. Pat. No.
6,545,824 issued in 2003 to Sensui Takayuki, discloses a
significantly improved lens optical system, in which the number of
lens elements is reduced to five along with a twice shorter length
of the system as a whole. Nevertheless, while preserving the
traditional structure, the lens optical system of U.S. Pat. No.
6,545,82 still remains large in size, heavy in weight, and
complicated in structure. These problems will always remain until a
wide-angle lens system is designed on traditional principles of
wide-lens system architecture.
[0015] A trend that appeared at the end of 90's put forward an
entirely new concept for the design of objectives that, on one
hand, could satisfy all the requirements of modern optical
objectives of high-quality photo cameras and, on the other hand,
could satisfy the requirements of miniaturization. For example,
modern digital cameras of megapixel's resolution have dimensions
from a matchbox to a cigarette pack. The size of the built-in
objectives makes it possible to arrange the entire objective within
the boundaries of the camera's casing. It is understood that
objectives of traditional design, i.e., those that use conventional
three- dimensional optical lenses, cannot be reduced to the
dimensions of a digital- camera objective without the loss of
quality. If one reviews the situation on the present market of
megapixel cameras, it can be seen that in this technique the amount
of pixels that can be used for obtaining an image is rapidly
growing from month to month while matching of the growing megapixel
capacity of the objective with the optical components without the
loss of image quality becomes more and more problematic. In
addition to photo cameras, the modules with integrating optics
assembly with the chip and wire assembly find application in such
products as cell phones, video phones, notebooks, computers, toys,
games, biometrics, etc.
[0016] Amkor Technology Co., Inc., Pennsylvania, USA, has developed
an Image Sensor Camera Module, which is a complete camera solution
that integrates an image sensor chip with DSP (digital processors),
optics, passive components, and flexible circuit. Using an advance
manufacturing solution, Amkor enabled the integration of chip and
wire assembly with the optics assembly. This resulted in a low cost
solution for a complete camera in a very small form factor with the
length of the objectives, including wide-angle objectives, of about
8 mm. However, such results were achieved due to the use of
traditional optical lenses having a very complicated shape with
variable-sign curvatures on the same surface of the lens. It is
understood that manufacture of such lenses requires the use of
complicated non-trivial technology. With further increase in the
pixel capacities of the CCD's or CMOS's the aforementioned
manufacturing solution may confront some limitations from the side
of optical component quality, especially if one tries to make the
optics flat.
[0017] On the other hand, development of optical fiber systems,
light-emitting diodes and laser diodes, systems of management,
control, and conversion of light beams in optical communication
systems, etc. gave impetus to developing new and efficient
microoptical systems such as microlenses, microobjectives,
collimators, etc. In principle of their operation and structure,
the aforementioned optical elements are the same as respective
traditional optical lenses, objective, collimators, etc., but are
intended for working with optical beams of small diameters, e.g.,
from several tens of microns to several millimeters.
Miniaturization of optical elements to the level of current
microlenses led to very stringent requirements with regard to
manufacturing accuracy and narrowed the allowable tolerances, e.g.,
on optical surfaces, to nanometric level. Recent success in this
technology made it possible to produce microoptical lenses with
very accurate aspherical surfaces.
[0018] A series of inventions made by Stephen Daniell (see, e.g.,
U.S. Pat. No. 6,721,101 issued in 2004) relates to the use of a
microlens optical system for obtaining a 3-D image in the
observer's sight. This technique is based on the principle of
creation of parallax between the "left" and "right" images, which
is perceived by the observer as a stereo effect.
[0019] The arrays used in the above inventions can be divided into
two categories. The arrays of the first type uses air as a
low-index material. Such arrays may be used, for example, in
illuminated displays of electronic image detection, machine vision,
and real-time 3D video capture. Arrays of the second use a
fluoropolymer as a low-index material, and convey a great
preponderance all incident light to the image plane.
[0020] More specifically, the system of U.S. Pat. No. 6,721,101 (as
well as the systems of all other inventions of Stephen Daniell) is
an assembly of two microlens array substrates, which in an
overlapped state possess better optical characteristics than a
single microlens array substrate. From the optical point of view,
this system functions as follows: an object located at a finite
distance from the observer is converted by the overlapped arrays
into an infinitely located image, which is observed with the
maximum possible angle of observation. This allows the observer,
who is located on the symmetry axis of a display, to clearly see on
this display two independent images of one object with the left and
the right eyes.
[0021] In reality, the Daniell's system does not widen the angle of
observation for the observer but rather creates a virtual effect of
stereovision. In this system, the second and third surfaces of the
array work as a separator of angles of incidence of light, i.e.,
starting from angle that exceeds a predetermined value, the light
does not pass through the system but is reflected on the principle
of total inner reflection, e.g., to the right eye, while the light
incident at smaller angles passes through the system, is focused on
the last flat plane of the lens system, and returns to the left
eye.
[0022] Although the Daniell's system cannot be used for widening a
real angle of observation and merely redistributes and divides the
optical path of light that passes through the system for stereo
effect, this system is a good example of a two-array assembly for
optical purposes. The use of a sandwich composed of two overlapped
film-like or plate-like arrays makes it possible to significantly
reduce the geometrical dimensions of the lens system, especially in
the optical axis direction.
[0023] The applicants made an attempt to solve the problems of the
prior-art technique by developing a flat wide-angle objective
having reduced longitudinal dimensions as compared to known
objectives with the same characteristics. This objective, which is
described in U.S. patent application Ser. No. 10/862,178 filed by
the same applicants on Jun. 7, 2004, is intended for creating
images with extremely wide angle of observation. The objective
consists of the first sub-unit, which is located on the object side
of the objective, intended for reduction of the field angle of
light incidence onto the objective, and comprises an assembly of at
least two microlens arrays with the same pitch between the adjacent
microlenses and arranged with respect to each other so as to
provide afocality, and second sub- unit that is located on the
image-receiving side of the objective and comprises an assembly of
conventional spherical or aspherical microlenses that create an
image on an image receiver. Each pair of coaxial microlenses of the
microlens arrays of the first sub-unit form an inverted
microtelescope of Galileo. The outlet aperture of a single
microtelescope is made so that spherical aberration can be
minimized almost to 0, while field aberrations can be corrected by
design parameters of the microlenses. The use of such an array of
microtelescopes makes it possible to significantly reduce the
overall dimensions of the first sub- unit of the lens system since
the longitudinal dimension of a unit telescopic cell of the array
is much smaller than the longitudinal dimension of a conventional
lens component used for the same function.
[0024] Although the aforementioned objective of U.S. patent
application Ser. No. 10/862,178 significantly reduces the overall
dimensions of the first sub-unit of the objective by replacing it
with a set of thin-film microlenses, the second sub-unit that
consists of conventional optical lenses still comprises a set of
four conventional lenses. In principle, the objective described in
U.S. patent application Ser. No. 10/862,178 can be realized with
the use of only two or three conventional lenses but this could be
done at the expense of the image quality that will be impaired
because of aberration that could not be completely eliminated.
These four lenses form a main factor that determines the overall
longitudinal dimension of the objective, which still remains
significant. Therefore, there is still enough room for improvement
in this direction.
OBJECTS AND SUMMARY OF THE INVENTION
[0025] It is an object of the invention to further reduce overall
dimensions of a flat wide- angle lens objective composed of a set
of microlens arrays with a set of only two traditional lenses. It
is another object to provide the aforementioned flat wide- angle
lens objective that provides the same image quality as the known
objective of this type with four traditional optical lenses. A
further object is to provide a substatially flat objective that can
be matched with CMOS, CCD, etc., and that can be integrated in an
image-sensor camera module.
[0026] A flat wide-angle lens system of the invention is intended
for creating images with extremely wide angle of observation. The
wide-angle lens system consists of two main sub-units, i.e., a
first sub-unit that is located on the object side of the objective
that comprises an assembly of two conventional negative aspheric
lenses, e.g., negative aspheric lenses having their flat sides
facing the object, and a second sub-unit, i.e., a set of four
microlens arrays arranged on the image- receiving side of the
objective and having the same pitch between the adjacent
microlenses. More specifically, the set of microlenses comprises a
pair of identical microlens arrays, the first micro lens array and
the second microlens array, interposed one onto the other with a
diaphragm array sandwiched between the aforementioned first and
second microlens arrays. The diaphragm array comprises a
light-impermeable matrix with micro-openings of a predetermined
diameter and with the same pitch as the aforementioned first and
second microlens arrays. The diaphragm array may be made
replaceable or may be applied as a permanent mask onto one of the
aforementioned microlens arrays. The aforementioned set of
microlens arrays further comprises a pair of additional identical
microlens arrays, i.e., a third microlens array and a fourth
microlens arrays. The third and fourth microlens arrays are located
on opposite sides of the aforementioned sandwich and are equally
spaced from the first and second microlens arrays, respectively.
The objective described above may have an angle field (2.omega.)
equal to about 60.degree.. The objective of the invention can be
realized into an optimal practical design only with predetermined
relationships between the parameters of the optical system that
forms the objective. The invention makes it possible to
significantly reduce longitudinal dimension of the objective.
[0027] In operation, the first sub-unit, i.e., the plano-concave
lenses, creates an imaginary image of the object in the focal plane
of the first sub-unit which is located on object side OB of the
objective 20, while the second sub-unit, i.e., the set of four
microlens arrays arranged on the image-receiving side of the
objective, creates an actual image of the object in the image plane
on the image- receiving side of the objective. In this case, the
aforementioned focal plane of the first sub-unit that contains the
imaginary image of the real object functions as the object plane
for the second sub-unit. This imaginary image is transformed into
an image of a real object in the aforementioned image plane of the
objective by the second sub-unit. In transition of the image from
the first sub-unit to the second sub-unit, the openings of the
diaphragm array limit dimensions of images created by the unit
microlens cells. In other words, the second sub-unit forms an image
of the real object in the aforementioned image plane of the
objective.
BRIEF DESCRIPTION OF THE DRAWINGS
[0028] FIG. 1 is an explanatory longitudinal sectional view of a
wide-angle lens system made in accordance with the invention.
[0029] FIG. 2 is a view in the direction from the image-receiving
side of the objective that shows hexagonal-lattice arrangement of
microlenses packing.
[0030] FIG. 3 is a view similar to in FIG. 2 that shows
orthogonal-lattice arrangement of microlenses packing.
[0031] FIG. 4 is a longitudinal sectional view of a unit microlens
cell.
[0032] FIG. 5 is a front view of a diaphragm array that shows
arrangement of diaphragm openings.
[0033] FIG. 6 is a longitudinal sectional view of the objective of
FIG. 1 in an assembled state.
[0034] FIG. 7 is a view illustrating optical ray traces for the
light beams passing through the sub-unit of two plano-concave
lenses included in the objective of the invention.
[0035] FIG. 8 is a view illustrating optical ray traces for the
light beams passing through the sub-unit of four microlens arrays
included in the objective of the invention.
[0036] FIG. 9 is a view illustrating optical ray traces for the
light beams passing from the input side to the output side of the
objective of the invention as a whole.
DETAILED DESCRIPTION OF THE INVENTION
[0037] A flat wide-angle lens system of the invention, which herein
after will be referred to as an objective of the present invention,
is shown in FIG. 1 which is a general longitudinal sectional view
of the aforementioned objective. The objective of the invention as
a whole is designated by reference numeral 20. The objective 20
consists of two sub-assemblies. The first sub-assembly 22 that is
located on the object side OB, which is on the left side in the
view of FIG. 1, comprises an assembly of two conventional negative
aspheric lenses 24 and 26, having their flat sides 24a and 26a,
respectively, facing the object side OB. The second sub-assembly 23
is a set of four microlens arrays 28, 30, 32, and 34 arranged on
the image-receiving side IP, which is on the right side of the view
of FIG. 1. Reference numeral 36 designates a diaphragm array, which
will be described later in consideration of the second sub-assembly
23.
[0038] Now the aforementioned sub-assemblies 22 and 23 of the
objective 20 of the invention will be described separately in more
detail.
[0039] As has been mentioned above, the sub-assembly 22 that is
located on the object side of the objective 20 consists of two
plano-concave lenses 24a and 26a. The lens 24a has a flat side 24a'
that faces the object side OB and a concave side 24a" that faces
the image-receiving side IP. Similarly, the lens 24a has a flat
side 26a' that faces the object side OB and a concave side 26a"
that faces the image-receiving side IP.
[0040] In order to describe the geometry and dimensions of the
objective components and their relationships, it would be
advantageous to designate and show the point of intersection of the
optical axis O-O with planes of the objective components
sequentially in the direction from the object side to the image-
receiving side IP. More specifically, these points of intersection
are shown in FIG. 1 as points "a" through "I" and correspond to
intersections of the optical axis O-O with the following components
of the objective 20: "a"--on the flat surface 24a', "b"--on the
concave surface 24a", "c"--on the flat surface 26a', "d"--on the
concave surface 26", etc. It is understood that the dimensions of
the lenses 24 and 26 and their relative positions will depend on
distances between the points "a" through "d" as well as on the
curvatures of the concave surfaces 24a" and 26a". These dimensions
and curvatures will be given later in Table 1 after description of
the second sub-assembly 23 with points of intersection "e" through
"I" with the optical axis O-O.
[0041] The second sub-assembly comprises a set of four microlens
arrays consisting of micro lens arrays 28, 30, 32, and 34 (FIG.
1),wherein the microlens arrays 30 and 32 are identical and
interposed back to back one onto the other. There is a diaphragm
array 36 sandwiched between the aforementioned microlens arrays 30
and 32. The aforementioned set 23 of microlens arrays further
comprises a pair of additional identical microlens arrays 30 and
34, which are located on opposite sides of the aforementioned
sandwich and are equally spaced from the microlens arrays 30 and
32, respectively.
[0042] Each microlens array consists of a plurality of microlenses.
More specifically, the microlens array 28 has a plurality of
microlenses 28a, 28b, . . . 28n on the side OB that faces the
object. The microlens array surface 28' of the microlens array 28
intersects the optical axis O-O in point "e". The side 28" of the
microlens array 28 opposite to the microlens array surface 28" is
flat and intersects the optical axis O-O in point "f". The surface
30' of the microlens array 30 that faces the object side OB has a
plurality of microlenses 30a, 30b, . . . 30n and is spaced from the
microlens array 28 at a distance given below in Table 1. The
surface 30' intersects the optical axis O-O in point "g". The
surface 30" of the microlens array 30 that faces the
image-receiving side IP is flat and intersects the optical axis O-O
in point "h". The side 32" of the microlens array 32 is flat and is
interposed onto the flat surface 30" of the microlens array 30. The
side 32" intersects the optical axis O-O in a point (not shown)
close to point "h" and spaced therefrom by a distance that is equal
to the thickness of the diaphragm array 36. Since the diaphragm
array 36 may have a thickness from several to several tenth of a
micron and may be applied as a mask onto one of the mating flat
surfaces, the aforementioned distance between the sides 30" and 32"
can be ignored, and it can be assumed that both interposed flat
surfaces intersect the optical axis in the same point "h".
[0043] The microlens array 34 has the microlens array surface 34'
that faces the object side OB of the objective 20 that intersects
the optical axis O-O in point "k". The surface 34' has a plurality
of microlenses 34a, 34b, . . . 34n. The side 34" that faces the
image-receiving side IP of the objective 20 intersects the optical
axis 0-0 in point "I". The microlens array 34 is spaced from the
microlens array 32 at a distance indicated below in Table 1.
[0044] It is important to note that all microlens arrays 28 through
34 have their microlenses arranged with the same pitch P and have
the same flat-lattice arrangement in all the lenses. In other
words, the microlenses 28a, 28b, . . . 28n have the same pitch and
arrangement as the microlenses 30a, 30b, . . . 30n, the microlenses
32a, 32b, . . . 32n, and the microlenses 34a, 34b, . 34n. However,
as will be seen from Table 1 given below, the microlenses 30a, 30b,
. . . 30n and 32a, 32b, . . . 32n of identical microlens arrays 30
and 32 have microlens curvatures different from those of the
microlenses 28a, 28b, . . . 28n, and 34a, 34b, . . . 34n of the
identical microlens arrays 28 and 34.
[0045] The arrangement of microlenses, e.g., of microlenses 34a,
34b, . . . 34n, when viewed in the direction of an optical axis
from the image-receiving side IP towards the object side OB, is
shown in FIG. 2 and FIG. 3, where FIG. 2 illustrates a
hexagonal-lattice arrangement, and FIG. 3 illustrates an orthogonal
arrangement. In FIG. 3, the microlenses are designated as 34a',
34b', . . . 34n'.
[0046] In all the microlens arrays 28 to 34 the microlenses are
coaxial. In other words, the microlenses 28a, 30a, 32a, and 34a are
coaxial and are arranged on the same axis O'-O' that is parallel to
the optical axis O-O. The same relates to the microlenses 28b, 30b,
32,b, and 32b, . . . 28n, 30n, 32n, 34n. This is shown in FIG. 4,
which illustrates a sequence of the coaxial microlenses of the
sub-assembly 23. The sequence of the type shown in FIG. 4 forms a
so-called unit microlens cell 23a for propagating a beam of light
in the direction from said object to said image plane.
[0047] FIG. 5 is a front view of the aforementioned diaphragm array
36. It can be seen that the diaphragm 36 has a plurality of micro
openings 36a, 36b, . . . 36n which have the same arrangement and
pitch P as the respective microlenses 28a, 28b, . . . 28n, 30a,
30b, . . . 30n, 32a, 32b, . . . 32n, and 34a, 34b, . . . 34n. The
microopenings 36a, 36b, . . . 36n are coaxial to the aforementioned
respective microlenses. The diameters of the microopenings 36a,
36b, . . . 36n of the diaphragm 36 should be smaller than the
diameter of a circle inscribed into the hexagonal or square
contours of the microlenses shown in the arrangements of FIGS. 2
and 3.
[0048] The distances between all the components of the wide-angle
objective 20 of the present invention and curvatures of the lenses
and microlenses are shown in Table 1 with reference to the
aforementioned points of intersections. It is understood that the
dimensions of the objective given in Table 1 relate only to one
specific example of the objective and do not limit the scope of
application of the invention.
1TABLE 1 Clear Point of Radii Thickness Aperture Refractive
intersection (mm) (mm) (mm) Index Dispersion (1) (2) (3) (4) (5)
(6) a 0.0000 0.500 4.00 1.77 49.6 b 0.3860* 0.500 3.40 c 0.0000
0.300 3.30 1.77 49.6 d 0.4984* 0.720 3.20 e 0.5800r 0.500 3.30 1.77
49.6 f 0.0000 0.220 3.30 g 0.3900r 0.500 3.30 1.77 49.6 h 0.0000
0.004 3.30 0.0000 0.500 3.30 1.77 49.6 i -0.3900r 0.220 3.30 k
0.0000 0.500 3.30 1.77 49.6 l -0.5800r 3.30
[0049] The radii (mm) in column (2) of Table 1 designate radii of
curvature on surfaces intersecting with respective points "a"
through "I". Since the curved surfaces 24a" and 26a" with points of
intersection `b` and "d" are aspherical, the curvatures indicated
in column (2) correspond to spherical components of these surfaces.
Sign "*" designates asphericity of the surfaces 24a" and 26a" with
constants K of asphericity being equal to K=-1 (parabolic) for both
surfaces 24a" and 26a". Symbol "r" designates microlens array. The
thickness in column (3) corresponds to the thickness between the
adjacent surfaces. For example, thickness 0.500 mm in the line "a"
corresponds to the thickness of the lens 24 between the points "a"
and "b". Thickness 0.300 mm in the line "c" corresponds to the
distance between points "c" and "d", etc. Clear aperture in column
(4) of the table is the so-called light aperture that approximately
coincides with the diameter of the lens in the conventional lens
and diameter of the entire microlens array in the case of the
microlens array. For example, clear aperture 4.00 mm in column (4)
of line "a" designates the maximal diameter of the lens 24 on the
surface 24a'. Clear aperture 3.30 mm in column (4) of line "e"
designates a diameter of the microlens array 32, etc. All optical
elements of the objective have the same refractive index, which for
the specific material and the dimensions of the lenses illustrated
here as an example is equal to 1.7. The same relates to dispersion
that in the illustrated example is equal to 49.6. The data of Table
1 corresponds to the hexagonal-lattice arrangement of the
microlenses with microlens pitch P=400 .mu.m.
[0050] It should be noted that with specifically selected
parameters, an example of which for a specific case is shown in
Table 1, each microlens array contains no more than a certain
amount of microlenses. For example, in the case of the parameters
of Table 1 the number of microlenses is about 100. It is important,
in this connection, to understand that the objective 20 of the
invention creates a real image of the object which is not a
discrete pixel-type image but a continuous image which in no way is
associated with the number of microlenses in the microlens arrays
28, 30, 32, and 34. This means that the dimensions of the second
sub-unit 42 have no design limitations in the transverse direction,
and that the transverse dimension of the objective is limited only
by the dimensions of the lenses in the sub-unit 40. In other words,
the objective of the invention can be matched with a CCD or CMOS
having any number of pixels.
[0051] FIG. 6 is a longitudinal sectional view of the objective 20
of FIG. 1 in an assembled state. The objective 20 shown in FIG. 6
is assembled from two pre- assembled sub-units 40 and 42. The
sub-unit 40 consists of the plano-concave lens 24 and the
plano-concave lens 26, of which the piano-concave lens 26 is
inserted into a thick cylindrical rim 44. The lens 24 is attached,
e.g., glued, to the end face of the cylindrical rim 44. The lenses
24 and 26 have a relative position that correspond to distances
indicated in Table 1. The second sub-unit 42 is composed of four
microlens arrays 28, 30, 32, and 34. The microlens arrays 30 and 32
are connected to each other, e.g., glued to each other, via the
diaphragm array 36 sandwiched between the microlens arrays 30 and
32, while two lateral microlens arrays 28 and 34 are connected to
the end faces of the microlens arrays 30 and 32 by gluing via
spacers 48 and 50, respectively. The spacers of the aforementioned
pre-assembled sub-units 40 and 42 are interconnected, e.g., by
gluing, e.g., via a spacer 52. The widths of the spacers 48, 50,
and 52 are selected so that the distances between respective points
"a" through "I" (FIG. 1) correspond to those indicated in Table
1.
[0052] FIG. 7 is a view illustrating optical ray traces for the
light beams passing through the sub-unit 40 of two plano-concave
lenses 24 and 26 included in the objective 20 of the invention.
Reference numerals IB1, IB2 . . . IBn designate input rays that
enter the objective 20 from the objective side OB. The
plano-concave lenses 24 and 26 create an imaginary image of the
object in their focal plane FP. It is understood that the
aforementioned image is located on the object side OB of the
objective 20.
[0053] FIG. 8 is a view illustrating optical ray traces for the
light beams IIB1, IIB2 . . . IIBn passing through the sub-unit 42
of four microlens arrays 28, 30, 32, and 34 included in the
objective 20 of the invention. The sub-unit 42 creates an actual
image of the object 20 in the image plane IP (FIG. 1 and FIG. 8) on
the image-receiving side of the objective 20. However, in this
case, a function of the object plane is fulfilled by the
aforementioned focal plane of the sub-unit 40 that contains the
imaginary image of the real object. In other words, the sub-unit 42
of four microlens arrays 28, 30, 32, and 34 forms an image of the
real object in the aforementioned image plane IP of the objective
20 with an image-transfer ratio of 1:1. This is achieved due to
appropriate selection of parameters for components of the second
sub-unit an example of which is shown in Table 1.
[0054] FIG. 9 is a view illustrating optical ray traces for the
light beams passing from the input side IB to the output side IP of
the objective 20 of the invention as a whole. In connection with
the operation of the entire objective 20, it is important to note
that in transition of the image from the sub-unit 40 to the
sub-unit 42, the openings 36a, 36b, . . . 36n of the diaphragm
array 36 limit dimensions of images created by the unit microlens
cells, such as the one designated by reference numeral 23a in FIG.
4.
[0055] Thus, it has been shown that the invention provides a flat
wide-angle objective with reduced dimensions and with the use of
only two traditional lenses combined with a set of microlens
arrays. The flat objective of the invention can be matched with
CMOS, CCD, etc., and can be integrated in an image-sensor camera
module.
[0056] Although the flat wide-angle lens system of invention has
been described in detail with reference to specific embodiments and
drawings, it is understood that these embodiments do not limit the
field of application of the invention and that any changes and
modifications are possible, provided they do not go beyond the
scope of the patent claims. For example, the number of lenses in
the second component may be different from those describe and shown
in this specification. The dimensions, pitch, sag, and other
characteristics of microlenses in microlens assemblies can vary in
a wide range. The microlenses and lenses of the second component
may be coated with anti-reflective coatings. The lens system or
objective of the present invention may be designed and calculate
for use with lights in invisible wavelength ranges, e.g., in the UV
and IR ranges. In the UV case, the lens arrays and conventional
lenses can be made from UV-grade quartz and special glasses,
magnesium fluoride, potassium fluoride, etc. In the case of IR, the
lens arrays and conventional lenses can be made from material with
high refractive indices, e.g., from germanium, etc. The numbers
given in Table 1 relates to a specific example described in the
present application. It is understood that similar objectives can
be made from materials other than those mentioned and with
different geometrical dimensions without departure from the scope
of the claims of the present invention. In that case, other numbers
will be contained in a table similar to Table 1. The microlens
arrays 30 and 32 can be formed as a single piece without the
diaphragm array. The wide-angle objective of the invention can be
easily matched with CCD's or CMOS image sensors with the diagonal
dimensions of about 3.2 mm.
* * * * *